Telecommunications system

ABSTRACT

A telecommunications system and a method for use in a telecommunications system is disclosed. The system comprises at least one station, means for determining the location of said station in said system, and means for providing information on said location of said station to a location service client The system is also provided with means for defining in dependence on information relating to the client, the accuracy of the location information to be provided to the client. Different accuracy classes

FIELD OF THE INVENTION

[0001] The present invention relates to telecommunications system and inparticular but not exclusively to a wireless cellular telecommunicationsnetwork.

BACKGROUND OF THE INVENTION

[0002] A cellular telecommunications system is based around cells orsimilar radio coverage areas. Examples of cellular telecommunicationssystems include standards such as the GSM (Global System for Mobilecommunications) or various GSM based systems (such as GPRS: GeneralPacket Radio Service), AMPS (American Mobile Phone System) or DAMPS(Digital AMPS) or third generation standards based typically on theWCDMA (Wideband Code Division Multiple Access), such as the UMTS(Universal Mobile Telecommunications System) etc. In general, a cellcoverage area or a base station coverage area of a cellulartelecommunications system can be defined as a certain geographicallylimited area covered by one or several base transceiver stations (BTS)serving mobile stations (MS) via an air or radio interface and usuallyconnected to a base station subsystem (BSS). Each of the coverage areascan be controlled by an appropriate controller apparatus. For example,in the WCDMA based systems each cell is controlled by at least one radionetwork controller (RNC) and in the GSM standard each cell is controlledby at least one mobile switching center (MSC). The controller isconnected further to a gateway or linking apparatus, such as a servingGPRS support node (SGSN) or gateway mobile switching center (GSMC),linking the cell to the: other parts of the communication system.Several cells cover a larger area, and form together the coverage areaof a cellular telecommunications network.

[0003] The mobile station (MS) or similar user equipment (UE) within oneof the cells of the telecommunications system is correspondinglycontrolled by the controller of the given cell. Even though the MS maybe controlled by only one controller at time, it may also be connectedsimultaneously to several controllers, e.g. when the cells overlap or inthe so called soft handoff mode, where the MS may be in simultaneouscommunication with two base stations, and those base stations may beconnected to different controllers. One of these controllers can bedefined as the serving (main) controller whereas the others act assecondary controllers.

[0004] In the context of the location of a mobile station, and thus theuser thereof, the use of cells or similar geographically limited radiocoverage areas and associated controllers facilitates the cellulartelecommunications system to produce at least a rough locationinformation estimate concerning the current location of an individualmobile station. More particularly, the cellular telecommunicationssystem is always aware of the current location of such mobile stationswhich are communicating with at least one of the base stations of thesystem and thus registered within at least one of the controllers of thesystem (i.e. are located within the area of one cell of the system).This information is available even when the mobile station is locatedwithin a coverage area of a visited or “foreign” network, as the visitednetwork is capable of transmitting the location of the mobile stationback to the home location register, e.g. for the purposes of routing andcharging.

[0005] This location information could also be used for other purposesthan solely for call processing (routing, charging, resource allocationetc.). There are several possible commercial and non-commercialapplications which could use this location information if it werereadily available. These possible applications include different localadvertisement and information distribution schemes (e.g. transmission ofinformation directed to those mobile users only who are currently withina certain area), area related WWW-pages (such as time tables, localrestaurants, shop or hotel guides, maps local advertisements etc.) forthe users of mobile data processing devices, location of those who havecalled to an emergency number and tracking of mobile users by anyone whowishes to receive this information and is legally entitled to obtain it.An application requiring precise and real-time location information ofthe movement of a mobile station is a mobile station movement predictionfeature that could be utilized, for example, in dynamic network resourceallocation. There are various other possible uses of the locationinformation and applications, which could use the location information.All applications, which need location information relating to thegeographical location of the mobile station, could find the locationinformation provided by means of a telecommunications system useful. Theusability of this location information could even be substantiallyincreased by improving the accuracy of the location information providedby the telecommunications system.

[0006] There is a proposal for a location service feature provided bymeans of a cellular telecommunications network which could provide thelast known location of a mobile station together with a time-stamp. Thisfeature can be provided by a separate network element or server whichreceives the information from the various controllers of the system. Forexample, in the GSM this information can be obtained from a VisitorLocation Register (VLR) of the visited MSC or the Home location Register(HLR) of the home network. This proposal would give the location to anaccuracy of one base station or cell, i.e. it would indicate that themobile station is (or at least was) within the coverage area of acertain base station or cell. When the last coverage area within whichthe mobile station is positioned is known by the system, an appropriateprocessor facility may then define the rough geographical location ofthe mobile station on the basis of the radio coverage area information.

[0007] The accuracy of the location determination can be improved byutilizing results of measurements which define the travel time (ortravel time differences) of the radio signal sent by the mobile stationto the base station. The measurements are preferably accomplished by atleast three different base stations covering the area in which themobile station is currently located. The measurement by each of thethree base stations gives the distance (range) between the base stationand the mobile station or distance difference (range difference) betweenthe mobile station and two base stations. Each of the range measurementsgenerates a circle centered at the measuring base station. Each of therange difference measurement creates a hyperbola (not a circle as in therange measurements). Thus if range differences are used in the locationcalculation, the intersections of the hyperbolas are searched for. In anideal case and in the absence of any measurement error, the intersectionof the three circles by the three base stations or the hyperbolas wouldunambiguously determine the location of the mobile station.

SUMMARY OF THE INVENTION

[0008] According to one aspect of the present invention, there isprovided a telecommunications system comprising at least one station;means for determining the location of said station; means for providinginformation on said location of said station to a location serviceclient; and means for defining in dependence on information relating tothe client, the accuracy of the location information to be provided tothe client.

[0009] According to a second aspect of the present invention, there isprovided a method for use in a telecommunications system comprising thesteps of determining the location of a station in said system; providinginformation on said location of said station to a location serviceclient; and defining the accuracy of the location information to beprovided to the client in dependence on information relating to theclient.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] For a better understanding of the present invention and as to howthe same can be carried into effect, reference will now be made by wayof example to the accompanying drawings in which:

[0011]FIG. 1 shows a schematic diagram of three radio coverage areas ofa cellular telecommunications system in which the embodiments of theinvention can be implemented;

[0012]FIG. 2 shows two radio coverage areas provided by sector antennas;

[0013]FIG. 3 illustrates one possible functional diagram for a locationserver; and

[0014]FIG. 4 shows a partially sectioned view of a mobile stationapparatus embodying the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Reference will first be made to FIG. 1 in which three basestations provide omnidirectional radio coverage areas 1, 2 and 3 of atelecommunications network. It is noted that even though theexemplifying telecommunications network shown and described in moredetail in the following uses the terminology of a GSM (Global System forMobile communications) public land mobile network (PLMN), it should beappreciated that the proposed solution can be used in any systemproviding communications between a transmitting station and a receivingstation. It should also be appreciated that even though FIG. 1 showsthree base station coverage areas, the invention can be implementedusing one, two or more than three coverage areas. The coverage areas 1,2 and 3 can also be, instead of base station coverage areas, three cellcoverage areas of the mobile telecommunications network, wherein thecoverage area of one cell can include more than one base station. It isalso possible to group cells such that one coverage area comprises morethan one cell (For example, an, URA (UMTS Terrestrial Radio AccessNetwork Registration Area) consists of a group of cells).

[0016]FIG. 2 shows two radio coverage areas 16 and 17 which consist ofsectors of base stations 14 and 15 provided with directional or sectorantennas. The base stations may use e.g. three 120° directional antennaswhereby three radio coverage areas are provided, or four 90° directionalantennas providing four radio coverage areas and so on, or anycombinations of different radio coverage beam widths.

[0017] In FIG. 1 each radio coverage area 1, 2 and 3 is served by therespective base transceiver station (BTS) 4, 5 and 6. More particularly,each base transceiver station BTS is arranged to transmit signals to andreceive signals from the mobile station (MS) 7. Likewise, the mobilestation 7 is able to transmit signals to and receive signals from therespective base transceiver station. The mobile station 7 accomplishesthis via wireless communication with the base stations. Typically anumber of mobile stations will be in communication with each basestation although only one mobile station is shown in FIG. 1 for clarity.Each of the base stations is connected to a respective networkcontroller (not shown), which in the exemplifying GSM system is a MobileServices Switching Center (MSC). It is noted that more than one basestation can be connected to each controller. Typically more than onecontroller is also provided in a network. The controller is connected toother elements of the network via a suitable linking or gatewayapparatus (not shown), such as Gateway Mobile Switching Center (GMSC) ora serving GPRS Support Node (SGSN).

[0018] The mobile station 7 is able to move from one coverage area toanother coverage area. The location of the mobile station 7 may thusvary in time as the mobile station is free to move from one location(base station coverage area or cell coverage area) to another location(to another coverage area) and also within one coverage area.

[0019]FIG. 1 also shows a Location Services (LCS) node 12 providingLocation (LC) services for different applications or clients 8 who areentitled to receive at least some degree of information concerning thelocation (or location history) of a mobile station. FIG. 3 illustratesin more detail one proposal according to ETSI (Europeantelecommunications Standards Institute) technical specification“Location Services” (T1P1.5/99-048r4) for the functional diagram of thelocation server 12. In general terms, the LCS functionality can bedefined as a feature capable of providing information concerning thelocation of the MS, and more particularly, the location defined on thebasis of the position of the mobile station relative to the basestation(s) of the mobile telecommunications network.

[0020] The location server node 12 is arranged to receive, by receivingmeans 30, predefined information concerning the location of the mobilestation 7 and to process this information and/or some other-predefinedparameters and/or to compute by processor means 31 appropriatecalculations for determining and outputting the geographical location ofthe given mobile station 7. The location server node 12 may alsocomprise a register or database 13 for storing radio coverage areaspecific data. This radio coverage area specific data can bealternatively stored in the base station itself or in the controllercontrolling the base station, from where it is transmitted to thelocation server node 12 for the calculations. The data is received fromthe telecommunications system by receiving means 30.

[0021] Even though not shown in detail, the location server node 12 canbe connected by means of an appropriate interface to the networkcontrollers (omitted from FIG. 1 for clarity but previously discussed)controlling the base stations signalling with the MS 7.

[0022] It is also noted that even though the location server node 12 canbe a separate node from a network controller, it could also be a part oran internal component or functionality of a controller, or gatewaycontroller or any other element of the telecommunications system.

[0023] The determination of the location of a mobile station can bebased on measurements of at least one feature of the received radiosignal. A feature which can be used in this is the time of arrival ofthe radio signal sent by the mobile station 7 at the base stations 4, 5and 6. The travel time of the received signal at any particular basestation is related to the distance travelled given by formula:

R=cT,   [1]

[0024] wherein

[0025] R=mobile to base station distance (range)

[0026] c=the speed of light, and

[0027] T=the travel time of the radio signal.

[0028] The location information can also be based on measurements madeat the receiving station to determine the signal strength, signal tonoise ratio or any other such feature of the received signal from whichit is possible to determine the distance between the transmittingstation and the receiving station. It is noted that the measurement ofthe feature of the radio signal can be accomplished in the uplink and/orin the downlink, i.e. at the base station end or at the mobile stationend or both. In case the mobile station is used for the measurements ofthe signal, it can use the radio network for sending the measurementresults to an appropriate network element. The necessary locationcalculations and determinations based on various collected/defined datacan be accomplished at the station (base station or the mobile station)or at an appropriate network element having an access to all requireddata.

[0029] In the situation illustrated by the three circles in FIG. 1 ortwo sectors 18 and 19 of a circle in FIG. 2 each distance measurementwould generate a circle or a sector of a circle, respectively, centredat the measuring base station and having a radius r equal to thetransmitting mobile station to receiving base station distance. In theabsence of any measurement error, the intersection of the three circlesof FIG. 1 and the intersection of the two circles of FIG. 2 woulddetermine the accurate location of the mobile station 7.

[0030] Alternatively or additionally, the geographical location isobtained from a reliable external source, e.g. from the well known GPS(Global Positioning System). The GPS system is a satellite based systemused in military and civil applications where accurate positioning isrequired, e.g. for the purposes of navigation. More accurate locationinformation can be obtained through a differential GPS. In addition tothe GPS, any other similar system capable of providing reliable locationinformation to the can be used for this.

[0031] The mobile station or the like 20 comprises an antenna 24 forreceiving the location signals from the GPS satellites or similarsystem. These signals are used by the mobile station 20 to determine thecurrent position of the mobile station 20 in a known manner. Thisdetermination can be accomplished by a processor 23.

[0032] According to one alternative the user of the mobile station 20inputs manually precise location coordinates (e.g. in altitudes andlatitudes, or by using street names or similar established addressinformation), e.g. by means of keys 26, a voice recognition device, orsimilar input interface.

[0033] The mobile station 20 of FIG. 4 is provided with another antenna22 for transmitting radio signals to and/or receiving radio signals fromthe base station BTS under examination. The mobile station can interfacewith the location server node 12 of FIG. 1 in several alternativemanners. Since it is capable of establishing a radio communication withthe base station, the mobile station may also use this radio interfacefor transmitting any messages and information to the location server orany other appropriate network element. The interface can also be aspecific infrared or short range radio connection (such as a “bluetooth”connection) or a fixed connection using e.g. appropriate plugs andsockets or cabling between the mobile station 20 and the locationserver. The mobile station also comprises a display 28.

[0034] It should be appreciated that any other suitable technique fordetermining the position of the mobile station can be used as analternative to the methods described previously. Method using Dopplershift techniques or time difference of arrival may be used. In someembodiments of the present invention, more than one method can be used.The location can be derived by the mobile station itself or by any ofthe network components. In either case, it should be ensured that themobile station or the network element has the required information todetermine the position of the mobile station. As will be discussedlater, different techniques for calculating the position of the mobilestation may be used at different times.

[0035]FIG. 3 schematically shows the location service model in which aLCS client 8 is arranged to request location information for one or morecertain target mobile stations 20 from the LCS server node 12. The LCSserver node 12 obtains positioning information obtained using one ormore of the techniques discussed previously or any other suitabletechnique. This information is provided to the LCS Client 8. Theparticular requirements and characteristics of a LCS Client 8 are knownto the LCS server 12 by its LCS client subscription profile. Theparticular LCS-related restrictions associated with each target mobilestation are detailed in the target mobile station subscription profile.The location service feature permits the location of a target mobilestation to be determined at any time whilst the MS is attached.

[0036] The LCS client 8 is a logical functional entity that makes arequest to the LCS server node 12 for the location information of one ormore target mobile stations. The LCS client 8 may reside in any entity(including a mobile station) within the PLMN or in an entity external tothe PLMN.

[0037] The LCS server node 12 consists of a number of location servicecomponents and bearers needed to serve the LCS clients 8. The LCS servernode 12 provides a platform which will enable the support of locationbased services in parallel with other telecommunication services such asspeech, data, messaging, other teleservices, user applications andsupplementary services. The LCS server node 12 responds to a locationrequest from a properly authorized LCS client with location informationfor the target mobile stations specified by the LCS client 8 ifconsiderations of target mobile station privacy are satisfied.

[0038] It shall be possible for the location determining process to makeuse of several sources of information in determining the location.Propagation and deployment conditions may limit the number or quality ofmeasurements or additional measurements may be possible. Some mobilestations may also have additional (independent) sources of positioninformation of the type discussed earlier. The LCS shall be capable ofmaking use of the restricted or the extra information as appropriate forthe service being requested.

[0039] The LCS Server 12 may provide the client 8, on request, thecurrent or most recent geographic location (if available) of the targetmobile station or, if the location fails, an error indication andoptionally the reason for the failure.

[0040] The following are examples of possible clients. Clientsbroadcasting location related information to the mobile stations in aparticular geographic area—e.g. on weather, traffic, hotels,restaurants; or the like. Clients recording anonymous locationinformation (i.e. without any MS identifiers)—e.g. for trafficengineering and statistical purposes. Clients enhancing or supportingany supplementary service, IN (intelligent network) service, bearerservice or teleservice subscribed to by the target MS subscriber. Theseare only examples and any other suitable clients may use the locationservice node. This service can of course be used to determine thelocation of a mobile station when it makes an emergency call.

[0041] The LCS Server 12 shall enable a network operator to charge LCSclients 8 for the LCS features that the network operator provides.

[0042] It may be possible for the LCS client 8 to specify or negotiate a(minimum) level of quality, such as accuracy, in a station locationinformation request. Different applications demand different levels ofpositioning accuracy and other positioning performance parameters, sothe levels of performance should be classified according to the type ofapplications. The quality of location information can involve parameterslike accuracy, update frequency, time stamp, time-to-first-fix,reliability, continuity, etc. The quality of the generated locationinformation can exceed the required level. In case location informationis not available to the required quality level, the request can eitherbe denied and the service execution terminated, or the user accepts thelower quality information. The quality level requirement of each service(application) could be set both by the subscriber and the serviceprovider.

[0043] It may be possible to select the repetition rate of the locationinformation update. The reports may be distributed to different clientsat different rates. It may be possible to identify and report when theuser's terminal enters or leaves a specified geographic area.

[0044] In one embodiment of the present invention, the classes arespecified for the accuracy of the positioning information, withestimated probability of correctness. Every measurement will usuallyhave a margin of error associated therewith. The classes should inpreferred embodiments of the present invention take into account forwhat purpose the positioning information is required. The selection ofthe class can be determined by each client or by each mobile station.The class selected can also take into account the type of service to beprovided by the client.

[0045] One benefit is for the user to define how accurate the locationinformation is which is made available to different types of LCS clients8. In one embodiment a logarithmic scale could be used, according towhich the accuracy is for 90% of cases within.

[0046] (10 cm-1 m No accuracy class)

[0047] 1 m-10 m Accuracy class A

[0048] 10 m-100 m Accuracy class B

[0049] 100 m-1 km Accuracy class C

[0050] 1 km-10 km Accuracy class D

[0051] 10 km-100 km Accuracy class E

[0052] “Not defined”—Accuracy class X

[0053] The US regulations require that when an emergency call is madethat the location of the mobile station be known to an accuracy of 50 m.This would fall into class B. As an alternative class B can be split intwo (or even more) classes: 10 m-50 m Accuracy class B1 and 50 m-100 mAccuracy class B2. Alternatively or additionally, any other class can besplit into two or more subclasses.

[0054] Class B could be used to identify that the user is in a givenbuilding so a service application can inform the user about thecompanies situated in this building or e.g. commercial servicesavailable in this building or area close by. Class D could be used toidentify users in a given town and class E to identify users in a givencounty or region.

[0055] Another way to define the accuracy classes may be (for 90% of thecases):

[0056] Class A: best achievable accuracy for the UE being positioned(whatever that may be)

[0057] Class B: small area, township, city block, around 1 km

[0058] Class C: somewhat bigger area, town, around 10 km

[0059] Class D: big area, region, around 100 km

[0060] Class E: coverage area of the visited PLMN in question

[0061] Class F: no position information to be given

[0062] Class L: location area

[0063] Class R: routing area

[0064] Class O: cell coverage area

[0065] Class P: PLMN area

[0066] Class X: not defined

[0067] One main use of the accuracy classes is to enable the user todefine wanted privacy levels. This means that the subscriber canindicate how accurate position information different LCS clients mayreceive.

[0068] Different LCS client types are defined, so that the user can thendefine his LCS privacy profile for example as follows:

[0069] “LCS Client of type Emergency center is allowed to get class ALCS information”

[0070] “LCS client of general Internet server type can get class B LCSinformation in general but class A only after asking me”

[0071] “LCS client type “family members” can get LCS information ofclass A”

[0072] “LCS client type “my company” can get LCS information of class?”

[0073] Another possible use of the accuracy classes is to enable theoperator to define location service tariffs for the client or the user:“Class A LCS accuracy will cost you x Euro every time when network isinvolved, Class B y Euro, class C is free of charge”, etc.

[0074] In summary embodiments of the present invention make use of thefeature that the geographical location of a station can be determined ina communications network with varying accuracy. The user of the station,or the network operator, will not automatically agree to communicate thebest achievable accuracy of the station location to any client.

[0075] The user of the station is able to restrict the accuracy withwhich the location of the station is communicated to different clients.The user of the station is able to define this accuracy differently fordifferent clients (types).

[0076] In embodiments of the invention the accuracy of the locationinformation of a station is defined with different accuracy classes.Different types of clients are defined. It is possible to define whataccuracy class is acceptable for the type of client. This combination ofaccuracy class per client type may be defined by the user or by thenetwork operator in the target station subscription profile.

[0077] In preferred embodiments of the present invention, there is aplurality of different methods available for determining the position ofthe mobile station. The method for determining the position of themobile station will be selected in accordance with the accuracy of theclass of position information.

[0078] It should be appreciated that whilst embodiments of the presentinvention have been described in relation to mobile stations of a mobiletelecommunications system, embodiments of the present invention areapplicable to any other suitable type of user equipment of other typesof systems providing location functionality. These system includesatellite based communication systems as well as satellite basedlocation systems.

[0079] The data can be transmitted between the various network elementin packet form. In alternative embodiments of the invention the data maybe sent in any suitable format.

[0080] The embodiment of the present invention has been described in thecontext of a TDMA system. This invention is also applicable to any otheraccess techniques including frequency division multiple access (FDMA)and code division multiple access (CDMA) as well as any hybrids thereof.It should also be appreciated that base stations can sometimes bereferred to as node B.

[0081] Embodiments of the invention may be used with fixed wirelineaccess network. Such networks can determine the approximate location ofthe terminal and hence its user by mapping the access point of theterminal to the network in geographical coordinates. In this way alsothe user of the fixed terminal can be offered services that are validand relevant for the geographical location of the user terminal. Thusembodiments of the present invention may be used with othercommunication systems where the users are connected to the network overfixed wire lines, since the geographical location of the access point ofthe fixed station can be determined with varying degree of accuracy.

[0082] In additional, the embodiments may also be used with varioussatellite based telecommunication systems.

[0083] It is also noted herein that while the above describes oneexemplifying embodiment of the invention, there are several variationsand modifications which may be made to the disclosed solution withoutdeparting from the scope of the present invention as defined in theappended claims.

1. A telecommunications system comprising: at least one station; meansfor determining the location of said station; means for providinginformation on said location of said station to a location serviceclient; and means for defining in dependence on information relating tothe client, the accuracy of the location information to be provided tothe client.
 2. A system as claimed in claim 1, wherein a plurality ofdifferent classes of location accuracy are provided.
 3. A system asclaimed in claim 2, wherein said classes are on a logarithmic scale. 4.A system as claimed in claim 3, wherein said scale is a log 10 scale. 5.A system as claimed in claim 4, wherein said classes includes at leastone of the following classes: 1 m-100 m 100 m -1 km 1 km-10 km 10 km-100km
 6. A system as claimed in claim 5, where at least one class isdivided into two or more subclasses.
 7. A system as claimed in anypreceding claim, wherein a user of the at least one station is arrangedto define the accuracy with which the location information is providedto the client.
 8. A system as claimed in any preceding claim, wherein aplurality of clients are present of at least two different types, theaccuracy of the location information provided to the client beingdependent on the type of the client.
 9. A system as claimed in anypreceding claim, wherein the accuracy with which the information isprovided is dependent on the type of service provided by the client. 10.A system as claimed in claim 2 or any claim appended thereto, whereinone class defines that no information is to be provided.
 11. A system asclaimed in claim 2 or any claim appended thereto, wherein one class isprovided for the case where no location information is available.
 12. Asystem as claimed in any preceding claim, wherein the costs associatedwith a service or function of the client is dependent on the accuracy ofthe location information.
 13. A system as claimed in claim 12, whereinthe costs are associated with the station.
 14. A system as claimed inclaim 13, wherein the costs are associated with the user or subscriberof the station.
 15. A system as claimed in claim 12, wherein the costsare associated with the client.
 16. A system as claimed in any precedingclaim, wherein one of a plurality of different location methods isselected to determine the location of the station in dependence of theaccuracy required for the location information.
 17. A system as claimedin any preceding claim, wherein said station is a mobile station.
 18. Asystem as claimed in claims 1 to 16, wherein said station is a terminalof a fixed wireline communication systems.
 19. A system as claimed inany of claims 1 to 16, wherein said station is a terminal of a satellitecommunication system.
 20. A system as claimed in any preceding claim,wherein a location service node is provided along with at least oneclient, said location service node being arranged to provided locationinformation with the required accuracy to the client.
 21. A method foruse in a telecommunications system comprising the steps of: determiningthe location of a station in said system; providing information on saidlocation of said station to a location service client; and defining theaccuracy of the location information to be provided to the client independence on information relating to the client.